[orange] Fix StringIO import to be compatible with python3

With this fix, the module still works with python 2.7
12 jobs for master in 1 minute and 20 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Build
failed #23667
build:2.7

00:01:03

failed #23668
build:3

00:01:20

 
  Test
skipped #23670
allowed to fail
lint:2.7
skipped #23674
allowed to fail
lint:3
skipped #23669
pyflakes:2.7
skipped #23673
pyflakes:3
skipped #23671
unittests:2.7
skipped #23675
unittests:3
skipped #23672
allowed to fail
unittests-modules:2.7
skipped #23676
allowed to fail
unittests-modules:3
 
  Deploy
skipped #23677
doc:2.7
skipped #23678
doc:3
 
Name Stage Failure
failed
build:2.7 Build
  File "./tools/local_install.py", line 30, in <module>
subprocess.check_call([sys.executable, os.path.join(dest, 'weboob-config'), 'update'])
File "/usr/local/lib/python2.7/subprocess.py", line 190, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/local/bin/python2', '/root/bin/weboob-config', 'update']' returned non-zero exit status 130
Weboob local installer

Installing weboob applications into ‘/root/bin’.
ERROR: Job failed: exit code 1
failed
build:3 Build

Installing weboob applications into ‘/root/bin’.
Traceback (most recent call last):
File "./tools/local_install.py", line 30, in <module>
subprocess.check_call([sys.executable, os.path.join(dest, 'weboob-config'), 'update'])
File "/usr/local/lib/python3.8/subprocess.py", line 364, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/local/bin/python3', '/root/bin/weboob-config', 'update']' returned non-zero exit status 130.
ERROR: Job failed: exit code 1